Measurement methods for quartz oscillators can be found in JIS C 6701, "Quartz Oscillators". FIG. 4 of the present application illustrates a circuit design of one such measurement method which includes measurement equipment 30 and test fixture 20. An oscillator 31 to be tested is connected to measurement terminals 26 of the main body of test fixture 20 and, thus, to the main body of a measurement equipment 30, via pi circuits 24 and 25 of test fixture 20. The main body of measurement equipment 30 typically includes impedance measuring equipment or a network analyzer for measuring the properties of connected oscillator 31.
In the case when the properties of oscillator 31 is to be measured with a serially connected load capacitance, the method as illustrated in FIG. 4 is modified. A printed circuit board 40 with an on-board load capacitance 11 is inserted between the main body of test fixture 20 and oscillator 31, as shown in FIG. 5.
FIG. 6 illustrates an overview of the actual components of FIG. 5. Note that FIG. 6 omits design details that are unrelated to the present invention. For more detail, one can refer to JIS C 6701, "Quartz Oscillators", Appendix 2, FIG. 3.
In FIG. 6, test fixture 20 includes connectors 27 for connecting to the main body of measurement equipment 30. A pressure plate 28 utilizes a spring (not shown) to press terminals 32 of oscillator 31 in the direction of connectors 27. The example in FIG. 6 shows both oscillator 31 and a printed circuit board 40 with an on-board load capacitance 11 being pressed toward connectors 27. In order to make contact with terminals 32 of oscillator 31, printed circuit board 40 includes printed contacts 41. The printed contacts for connecting the main body of test fixture 20 with printed circuit board 40 are provided on the back side of printed circuit board 40 (the surface that is not visible in FIG. 6).
As described above, pressure plate 28 is employed to press oscillator 31 and printed circuit board 40 together. Each time a different oscillator is tested, a new pressing operation is required on both printed circuit board 40 and the new oscillator to be tested. Furthermore, for measurement items for which a load capacitance is not required, it is also necessary to remove printed circuit board 40 and directly attach oscillator 31 to the main body of test fixture 20 (i.e., direct coupling). As a result, such an arrangement increases the number of steps for attaching oscillator 31 and printed circuit board 40.
It is also known that there is a method for inserting a load capacitance configuration or a direct coupling configuration in the measurement circuit by opening or closing a switch connected across the load capacitance. This method is found in JIS C 6701, "Quartz Oscillator", Appendix 3, FIG. 1. Although the actual switching operation in this method is simplified, the physical size of the switch has the disadvantage of increasing the size of the main body of the test fixture and the overall cost of the measurement system.
There is a desire to decrease the operational steps for exchanging different oscillators to be tested and for switching between a load capacitance configuration and a direct coupling configuration, without increasing the overall size and cost of the measurement system.
Accordingly, an object of the present invention is to improve the operations for attaching and removing the oscillator to be tested and the printed circuit board.
It is a further object of the present invention to improve the operations for switching between a load capacitance configuration and a direct coupling configuration.
Another object of the invention is to provide the above improvements to the measurement system at a low cost.